The present invention relates to processes for preparing thermoplastic composites. More particularly, the present invention relates to processes for preparing composites of a polycarbonate with an elastomeric siloxane-polycarbonate block copolymer.
Safety glazing or penetration resistant glazing for structural items such as windows, windshields and the like including multiple glass and/or high-strength polymeric structural layers are well-known. Glass and polycarbonate resin laminates are disclosed in U.S. Pat. No. 3,666,614, the glass and polycarbonate being sealed or joined together by an ethylene-vinyl acetate copolymer. In U.S. Pat. No. 3,520,768, there are disclosed laminates of relatively thick glass sheets with a thin polycarbonate foil disposed between the glass sheets as the cohering material. Also known (from U.S. Pat. No. 3,979,548) are laminates wherein self-healing, chemically resistant polyurethane films or layers are adhered to glass. U.S. Pat. No. 4,027,072 discloses laminates comprising polycarbonates and siloxane polycarbonate block copolymers and glass in various combinations and in which an ultraviolet, mar resistant, hard coat is utilized on at least one external surface or both external surfaces of such laminates. U.S. Pat. No. 4,204,026 discloses glass-polycarbonate laminates wherein the glass and polycarbonate are bonded together by a bonding system comprised of an aminoalkyl tris[poly-(aryloxysiloxane)] primer and a siloxane-polycarbonate block copolymer bonding agent. U.S. Pat. No. 4,312,903 discloses multi-ply laminates which contain polycarbonate layers bonded into the laminates with a siloxane-polycarbonate block copolymer. These last-mentioned laminates are particularly useful in structural items such as bullet resistant glass, windshields, windows and as transparencies for gas masks and the like. It is normal practice in constructing certain of such laminates to utilize glass or relatively hard solid resinous materials as impact- or shock-receiving layers and to utilize polycarbonate as the layer presented to the person or object being protected.
The above-described laminates have been prepared by so-called "laying up" of the laminate. Such laying up involves physically placing the individual sheets in contact with one another and bonding them together by means of heat and pressure. This procedure suffers from certain disadvantages. The laying up procedure is often done by hand or is only semi-automated and thus is labor intensive. In addition, it is difficult to exclude airborne particulate matter from the sheets during the laying up procedure. When trapped between the sheets, such particulate matter decreases the optical clarity and aesthetic appearance of the laminate and, in extreme cases, can lead to subsequent delamination.
A need exists for an efficient method for preparing such laminates which reduces the overall labor requirement and which minimizes the chances of trapping contaminating particulate matter within the laminate.